Thermionic valve



April 25, 1933. H. w. HOUCK THERMIONIC VALVE Filed July 18, 1924 3 Sheets-Sheet l INVENTOR I44 How/v:

ATTORNEY April 25, 1933. H. w. HOUCK THERMIONIC VALVE Filed July 18, 1924 3 Sheets-Sheet 2 ATTORNEY H. W. HOUCK THERMIONIC VALVE Filed July 18 1924 April 25, 1933.

3 Sheets-Sheet 5 INVENTOR fl/i/mv h. f/oucrr ATTORNEY Patented Apr. 25, 19 33 UNITED STATES PATEN oFFIcE HARRY XV. HOUGK, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO DUBILIER CONDENSER CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE THERMICONIC VALVE Application filed July 18, 1924. Serial No. 726,841.

This invention relates to improvements in thermionic valves for use in electrical circuits, and especially for rectifying alternating electric currents.

An object of this invention is to provide a thermionic valve in the'form of a container from which the air has been exhausted and which encloses an anode and a plurality of independent heated cathodes adapted to co-operate with said anode in a manner that will afford the results which it is desired to attain. I

The nature of my invention is fully set forth in the following description taken with the accompanying drawings and the precise novel features are defined in the appended claims. But the disclosure of the invention herein is, of course, intended as illustrative only, and I reserve the right to make changes within the scope and spirit of my invention as widely as is permitted by the broad and general meanings of the terms in which the claims are expressed.

On the drawings,

Figure 1 is a diagrammatic view showing the essential construction of one form of a thermionic valve according to my invention;

Figure 2 shows another form applicable for the rectification of alternating currents from three phase supply.

Figure 3 shows a circuit by means of which a thermionic valve according to my invention can be made to serve its intended purpose;

Figures 4, 5 and 6 are respectively an end view, a side view and a bottom View showing the actual mechanical construction of a vac uum tube or container enclosing an anode, and a plurality of cathodes, constituting a thermionic valve according to my invention. Figure 7 is a perspective view of the shape of the anode of such a thermionic valve;

Figures 8, 9 and 10 are views similar to Figures 4, 5 and 6 respectively, showing a modified form of thermionic valve; and

Figure 11 shows a further modification.

On the drawings, the same numerals identify the same parts throughout.

Referring first to Figure 1, I show at B a container such as a so-called bulb or vacuum tube from which the air has been removed. This bulb maybe of glass and it encloses two independent cathodes in the form of emissive filaments F1 and F2; and associated with these two filaments and preferably disposed between them is an anode such as a plate P. The anode P is joined to a conductor W leading from the inside to the outside of the tube, andsealed therein. Similarly each of the filaments is connected at its extremities to separate lead wires or conductors IV leading to the exterior of the tube or container B, so that the electrodes of the valve can be joined to an electric circuit, in the desired manner, when needed for use. The filaments F1 and F2 can be of metal of any high melting point and of suitable properties, suitably pre treated, for instance, with a coating of an oxide or mixed oxides of suitable alkaline earths. WVhen heated to the requisite temperature such filaments are productive of a relatively large electron emission with a relatively small expenditure of power. By connection to a suitabletransformer and causing the two hot filaments F1 and F2 to be alternately at adequate negative potential with respect to the cold plate P, currentwill be made to flow from the plate or anode P to each cathode or filament F1 and F2 in alter nation, and thus the rectification of both half'waves of an alternating current can be accomplished.

In Figure 3, I show a complete means by which alternating current can be so influenced by the operation of such a valve as to be converted into direct current. In this view, I represents the primary of a transformer which may be joined to a source of alternating current, for instance, an ordinary lighting or power circuit in a business structure or dwelling. Usually the alternating current supplied to the circuit connected to tl e primary winding I may be taken as changing at the rate of 60 cycles per second, but a more or ess rapid alternation of the current, in so far as it influences the rectification of the tube is immaterial, and will answer as well, as the invention is not restricted to the use of alternating current of any par ticular frequency. This primary winding I, as shown, is placed upon the core of magnetic material M, with the overlying secondary winding S in inductive relation thereto, on the same core, with the secondary winding S tapped at its midpoint; and preferably at each end of the same are two windings T1 and T2, one of which has its terminals united to the leads of one of the filaments F1, and the other of which has its two termi nals united with the leads of the other filament F2. In the single phase rectifier between these two filaments is a broad plate or anode P, the filaments and the plate being enclosed in an evacuated bulb B, and the plate being united b the condu or W to the midle point of the secondary S. In addition to the conductors which unite the filaments to the coils T1 and T2, I employ conduct 1' 201, leading from the upper end of the coil S, for example, in Figure 3, to one terminal of the upper filament I while from the opposite extremity or terminal '5 he secondary wind-- ing S extends a sim ar conductor 102 to one terminal or extremity of the other filament F2. In the line of the conductor V joining the plate to the middle of the secondary S, is interpolated a condenser C, and the opposite plates or terminals of this condenser are joined to a pair of leads L, by which the rectified current is conducted to the load or power utilizing apparatus. If desired, the c011- denser may be omitted.

The above described circuit connections with the single anode, independent multiple cathode bulb B constitutes a complete means for converting and rectifying alternating current, for energizing the filaments of the valve B, and for causing both half waves of such current to flow in the output leads in one direct-ion only.

As is well-known in all vacuum tubes of this general class, the emission of electrons between filament and plate can occur only when the filament is at a negative potential, and the plate is a positive potential.

It then to the filaments F1 and F2, there is applied alternately a potential which is negative wit-h respect to the potential of the plate P, current will flow from the plate P in the tube B. first to one filament and then to the other, but always returning to the plate in the same direction by the conductor lV joined to the middle of the secondary winding S. Hence, each half cycle of alternating current will charge the condenser, which delivers its stored energy with greater or less rapidity to the load circuit, the resulting current having a unidirectional pulsatory form, the amplitude of the pulses depending upon the char acteristics of the smoothing devices employed. For instance, suppose the secondary winding S is excited so that at a given instant its upper terminal is of positive poten tial, and its lower terminal is negative,-as indicated by the curved line V1, representing the voltage distribution along the length of this winding. Under such circumstances, the upper filament Fl, which is joined by the wire 101 to the upper end of the secondary winding S, will be too positive, with respect to the plate, in potential to permit the passage of electrons from it to the plate P. Hence, no current will flow from the plate to the upper filament Fl. But as the other end terminal of the secondary winding is negative, with respectto the plate during this half cycle, the filament F2 connected to this secondary terminal, will be negative. Thus the current will flow in the valve B from the plate to the filament l and along the conductor 102, to the lower end of the secondary, and through the secondary to the middle thereof whence it hot. s, by way of the central wire or conductor W. On the inserthm ot the reservoir condenser C of large capacit in the lead l etween the mid-secondary and anode plate, the condenser becomes charged, that terminal of the condenser which is connected to the secondary being the positive terminal, while the 1' terminal of the condenser connected to the anode plate becomes the negative pole or terminal. Hence, as soon as the voltage of the secondary charging E. M. F. becomes less than that of the charged condenser, he latter ilmnediatoly be gins to discharge through the leads L, which are, of course, connected to the work circuit in which. the rectified current is utilized. A t 180 degrees later in the cycle, conditions will have so changed that the lower terminal of the secondary has become positive and the upper terminal negative, as indicated by the broken curved line V9, representing the intensity of voltage distribution along the length of the coil S at the end of the next halt cycle. Now the lower filament F2 is too positive for any current from the plate to flow across to it in the bulb B and current passing through the bulb must take the path provided between the plate P, and the upper filament F1, and along the wire wl to the upper extremity of the secondary and from the mi ddle thereof to the condenser, along the wire W. The condenser is then charged as before and sends another impulse of current in the same direction through the leads L. Thus the condenser is repeatedly and very rzmidly charged, and more or less slowly discharged through the leads L, and the condenser terminal directly connected to the mid-secondary is always positive, while the condenser terminal on the side of the bulb, and connected to the anode plate, is always the negative terminal. Therefore, the impulses of current in the leads L are always in the same di 'rection and both halves of the alternating current wave are rectified and converted as required.

The filaments F 1 and F2 are suitably heated by the current which is induced by the coils T1. and T2, and these coils T1 and T2, being connected by one lead to the respective secondary H. T. terminals, are, of course, suit ably insulated from the transformer primary and core M.

Instead of the parts consisting of the trans former and the associated coils for the heating of the filaments, I may employ other circuits for rectifying alternating currents by means of a thermionic valve according to this invention. Such further use of my invention is indicated in Figure 2 which presents another form of valve consisting as before of a container from which air has been exhausted, but having the two filaments F1 and F2, another filament F3, and a hollow plate of prismatic cross section, so that rectification of three-phase alternating currents can be pro duced. With this tube, the connections will be so made that current will flow from the plate to each of the filaments in turn, the plate to be oined to the common terminal of any three-phase star connected circuit, and each of the filaments, to one of the remaining terminals, the filaments to be heated to a suit able temperature in any feasible way.

The invention herein set forth is intended for the rectification of currents to be used in the art of signaling by radio, but I may, of course, employ it to convert alternating cur rents for any other purpose.

If the condenser C is not utilized, the midpoint of the secondary S is joined to one lead L and the plate P to the other.

To employ the principle and gain the objects of this invention, the thermionic valve or vacuum tube B should preferably be constructed in the manner indicated in Figures 4 to 10 inclusive, the container appearing in Figures 4, 5, 8 and 9 as if broken away to show the anode and cathodes inside. In this design of vacuum tube the anode or plate P has a large surface area, so that the heat of operation can be radiated, and the temperature of the anode thus controlled; while the cathodes are mounted to the best advantage, with the plate P always between them and so supported that they are maintained in the the exact relation required, and especially prevented from getting displaced or becoming loose when the valve is in operation and current is flowing through these cathodes or filaments F1 and F2.

Referring first to Figures 4, 5, 6 and 7, I show the bulb or container B aflixed at one end to a metallic sleeve 1 to serve as the base or plug of the tube, which is adapted for insertion into a socket and for thus enabling the tube to be supported in operative position. On its interior, the bulb B has a projection 2 of glass or other insulation for holding the parts which support the anode P and the cathodes F1 and F2 and the conductors which connect these parts to the ex terior of the bulb. The numeral 3 indicates a pair of bent wires forming a yoke or mounting, the arms of this yoke being secured to the plate P, and the lower ends of the wires constituting the yoke, providing the same with a shank, are embedded in the projection 2, so as to hold the anode P in place. Preferably this anode or plate P is hollow and has the form of a fiat open-ended tube, as indicate in Figure 7, the anode and filaments being shown in edge view on F igure 4, and in face view on Figure 5. The cathodes or filaments F1 and F2 are at each side of the anode or plate P, the wide faces of the anode P being interposed between the cathodes so as to shield one from the other, and prevent leakage from one of the filaments to the other, and thus confine the stream of electrons from each cathode to the space between said cathode and the adjacent wide face of the anode P and the area enclosed bet-ween the two arms of each filament is less than the area of the adjacent face of the anode P. Embedded in the projection 22, like the shank of the yoke 3, are supports 4, in the form of wires or metal rods on each side of the anode P, and extending parallel with the opposite wide faces of the anode P. The upper or outer ends of each of these supports or mountings 4 are turned over towards the anode P and bent to provide hooks 5, so that the cathodes can be looped over these hooks. The cathodes Fl and F2 are thus located between the anode P and the supports 4; and likewise embedded in the projection 2 are pieces of wire 6 or the like, two on each side of the yoke 3, and each pair of the pieces 6 being directly beneath the adjacent cathode. One of these pieces 6, of each pair, is connected to one of the lower ends of the adjacent cathode, and the other of the pieces 6 being connected to the other lower end. Each of the filaments will, therefore, extend from one of the pieces of wire 6 up over the hook 5 of the adjacent support 4 and down to the other piece of wire 6. The bottom of the base or plug 1 will be closed with insu lation and in this insulation will be embedded contact points or studs so that current can flow to the two filaments F 1 and F2.

The pieces of wire 6 connected to the ends of the filament F1, for example, will be joined by conductors WV passing through the base 1 to contact studs f1; while the wires 6 joined to the ends of the other filament F2 will be connected by similar conductors W to two contacts studs f2 projecting from the bottom of the base. The plate or anode P will be joined through the yoke 3 by aconductor \V, which is united to the shank of the yoke, to the base 1, so that the plate P will be in circuit through a conductor attached to this metallic base. On the side of the base will be a stud 7 to co-operate with the usual bayonet slot to hold the bulb in the socket which receives it. The anode P is of course of some metallic conductive substance, and the filaments F1 and F2 are, as above stated, parallel to the opposite wide faces of this anode throughout their length. The opposite faces of the anode are of greater breadth than the greatest distance between the legs of the filaments at the lower ends thereof where they are joined :o the wires 6. Hence, the filaments are shielded one from the other and no leakage can take place between them. At the same time, the large surface area of the plate enables it to radiate heat effectually and the temperature thereof is thus kept within proper limits. If desired, the anode P could be closed at both ends and could be cooled by means of pipes extending through the bulb and the walls of the plate, so as to permit the circulation of a cooling agent such as water or air, through the same.

The same is true of the form of ano-rje shown in Figure 2, which is hollow, like the plate shown in Figure 7, and has three face. with a cathode F1. F2 and F3 opposite each face and parallel therewith.

The upper ends of the supports 4 Carry; the hooks 5 are resilient and have sufliczent tension to keep the filaments Fl and F2 tautand prevent them from getting slack. Hence, the filaments or cathodes are always main-- tained in exact position with respect to the opposite wide faces of the plate P, and the required distance from these faces, and when they become heated through passage of current and expand somewhat, the resilience of the upper ends of the supports l compensates for the increase in the lengths of these filaments and draws them tight.

Figures 8, 9 and 10 show the same type of tube except that the elongated supports 4 are dispensed with, and in their place, I employ a rod 8 passing through the middle of the anode P and embedded at its lower end in the projection 2. The rod extends above the upper end of the anode and carries a bea d 9 of insulation, such as glass, from the oppo sides of which project pieces of spring wire 10. the ends of which carry looks 5 over which the filaments are looped as before. The pieces of spring wire 10 also serve means to keep the filaments tight and prevent slack. taking up automatically any increase in the length of the filaments as they expand on increase in temperature.

In Figure 11 the anode P2 is in the form of a double tube, the two parts of which are joined together, with the filaments coiled or otherwise disposed inside of same. This anode more eificaciously shields on filament from the other.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States 1s:-

1. A thermionic valve having an anode, and a plurality of cathodes co-operating with said anode, the cathodes having the anode be tween them, the anode being hollow and hav ing a plurality of exterior faces, each of said faces being parallel with and adjacent to one of said cathodes, said faces being of relatively large area with respect to the cathodes, and means supporting the cathodes under tension to keep them in position with respect to the anode and having such dimensions as to provide a minimum spacing between the anode and cathodes.

2. A thermionic valve having a common anode in the form of a hollow body with wide exterior faces, a plurality of cathodes positioned adjacent to and extending parallel with said faces, the anode being positioned. intermediate said cathodes and extending in overlapping relation thereto to shield the cathodes from each other, and means supporting sa d cathodes extending through said hollow anode.

3. A thermionic valve having a common anode, a plurality of cathodes, said anode having the form of a hollow rectangular body with wide exterior faces, each of said cathodes being adjacent to and parallel w th one of said faces, the anode being positioned intermediate the cathodes and extending in overlapping relation thereto to shield the cathodes from each other, and means extending through said anode and supporting the cathodes in insulated relation to each other and to the anode.

l. A. thermionic tube comprising a plurality of cathodes widely spaced within said tube, a metallic plate closely adjacent to and parallel with each of said cathodes and e. tending beyond the cathodes, the said plates being oined together and forming a hollow anode substantially fiiling the space intermediate said cathodes and a support for said cathodes disposed between said plates.

5. A thermionic tube comprising two filamentary cathodes in spaced parallel relation, an anode disposed between said cathodes having two portions spaced apart and parallel with said cathodes, each of said anode portions being closely adjacent to one of said cathodes. a support extending between said anode portions. and spring members carried by said support and electrically insulated from each othe. said spring members engaging the respective cathodes.

6. A thermionic tube comprising two lilamentary cathodes having divergent legs disposed in parallel planes, a metallic plate closely adjacent to and parallel with each of said cathodes, said plates being spaced apart and disposed directly between said cathodes, a support extending between said plates, and resilient members carried by said support and electrically insulated from each other, said resilient member engaging the respective cathodes.

In testimony whereof I afiix my signature.

HARRY W. HOUCK. 

